Telephone system



Aug. 18, 1931. K. KQPARSSQN 1,319,683

Tamradna. SYSTEM Filed June 9, 1930 INVEN {L .87 hum/ o Patented Aug.18, 1931 KNUT LARSSON, OF STOCKHO'LM, SRTEDEN,

.kSSIGNOB. TOTELEFONAKTIEBOLAGET L. M.

ERICSSON, OF STOCKHOLM, A COMPANY OF SWEDEN TELEPHONE SYSTEM Applicationfiled June 9, 1930, Serial No. d60,017,-and. in Sweden June 21, 1929.

in telephone plants 01 system the subscribers lines are usually providedwith so called line and cut-ofli relays to control the call circuit and,in certain cases,

5 also the call meter circuit. The cost of said relays makes up aconsiderable part of the total costs for a telephone exchange, as

counted per subscribers line, for which reason any simplification in theconstruction of such relays may considerably influence the economy ofthe entire plant.

The present invention has for its object to reduce the cost ofmanufacture of the line and cut-ofii relays by a reduction in the numberof contact springs of said relay. This is brought about according to theinvention by that those contact springs of the cut-off relay, whichcontrol the circuit extending over the test wire, are adapted to beactuated by the 29 line relay when the latter is energized.

The invention will be more closely explained with reference to theaccompanying drawings, on which Figure 1 shows a known arrangement ofthe line and cut-oil. relays and the appertaining circuits whereasFigure 2 shows a corresponding arrangement according to the invention.Figure 3 discloses an example of the constructional features.

Figure 1 shows a subscribers line of which the two branches a, I)together with the appertaining test wire 0 are connected to fixedcontacts alc, bk, 07a in the contact field of a call finder. To thesubscribers line belongs the line relay LB, 2. cut-on relay BR and acall meter SM.

Upon a call, the line relay LR is energized in known manner over thesubscribers line, a call finder being started through the intermedium ofthe starting relay SR the circuit of which is closed over the contacts8, 9 of the line relay. At the same time the cut-off relay BB isconnected to the test wire 0 over contacts 10, 11 of the line relaybesides which the call meter SM is disconnected from the test wire 0 atthe contacts 12, 18. When the call finder finds the calling line acircuit is closed over the test wire 0 and the contacts 10, 11 throughthe cut-off relay BR which is energized and disconnects the line relaythe central battery LR at the contacts 1, 2, 3, 4c. The line'relay LR-is deenergized and opens the circuit of the relay SR. The cut-oil relayBR remains thereupon energized over the contactsf), 6

whereas the call meter now is disconnected at the contacts 6, 7.

Call'metering may also be brought about in known manner by connectingthe wire 0 to the negative pole of the battery, the cutoff relay BRbeing short-circuited. When the relay BR for this reason is deenergizedthe call meter SM is connected into circuit to the test wire over thecontacts 6, 7 the call meter being then actuated.

The circuit arrangement shown in Figure 1 may according to the inventionbe simplified in a manner shown in Figure 2. The group of contactsprings 5, 6, 7 is here so disposed that it may be actuated by both thecut-0E relay BR and the line relayLR. Hereby the contact spring group10, 11, 12, 13 marked in Figure 1 by a dashed and dotted circle becomessuperfluous at the same time as the circuits are simplified. The samecontact spring couple 5, 6 over which the cutoff relay is connected tothe test wire serves namely also to lock the cut-off relay after thelinerelay LR is dc-energized. Further, only one contact spring couple 6, 7is required to control the circuit of the call meter SM. For the rest,the arrangement is the same as in Figure 1 and the operation is also substantially the same. When the line relay LR is energized the contactspring group 5, 6, 7 is actuated in such a manner that the cut-oil relayBB is directly connected to the test wire, whereas the call finder SM isdisconnected. As said contact spring group is adapted to be actuatedalso by the cut-0E relay, said group will be held in the actuatedposition by the relay BR even after the line relay LR has beendeenergized. The call metering then takes place in the same manner asabove by short-circuiting the relay BR over the test wire, the callmeter SM then obtaining a current impulse over the contacts 6, 7.

Figure 3 shows an example of the disposition of the contact springs ofthe relays LR and ER. The contact s )ring group 8, 9 and 1, 2, 8, 1 areso dispose that they are actuated only by the relay armatures LA and BArespectively Whereas the contact spring group 5, 6, 7 is disposedbetween said groups so that it may be actuated by both armatures.

5 I claim:

1. In a circuit arrangement for telephone plants a subscribers line,line and cut-oft relays connected to said line, a number of contactsappertaining to said cut-off relay and 1 controlling,the circuitextending over the test Wire, and means to actuate said contacts by theline relay when the latter relay is energized.

2. In a circuit arrangement for telephone 1 plants, a subscribers line,line and cut-ofi' relays connected to said line. a number of cont'actsappertaining to said cutoff relay, means to actuatesaidcontacts' by theline relaywhen the latter relay is energized, means 2q to' c'onnect. thecut-off relay to thei test Wire "over contacts Which are actuatedbytheline relay when it is energized, and means to lock sziidbutpfirelaycyerthesame contacts When it islene rgiz ed'o'ver the test wire.

3.;In a circuit arrangement according to "claim 2, means to disconnectthe call meter from and connect itto thetest Wire over one and the samebreakcontact actuated both bythe line relay and the cut-off relay.

In ,te stimonyrwhereofl ,afllx my signature.

4 KNUT LARSSON.

